exporting earths

[johnnyjb]

Hi ive been doin a little searching here on exporting earths and need a bit of clearing up.

Am i wrong to believe if a house is pme and you supply a shed ,you must not usually connect the earths due to different potentials between the buildings .Drive a rod for shed and make it tt. Can you export the pme earth and use it as earthing in the shed if you bond metallic objects in the shed.

Sorry but i mightnt make sense or be totally off the mark but im tired and trying to do a project.Any other info would be grateful
Thanks.

 

[Spark123]

Depends on what there is which requires bonding, you would only bond extraneous conductive parts. These bonds need to be adequately sized as a Main equipotential bonding conductor hence if you need a 10mm bonding conductor you can either run a MEB back from the ECP to the MET or if the supply CPC is adequate for use as a MEB that may also be used - if using the SWA armour you need to correct for the different material. Also, MEBs should not exceed 0.05 ohms.

 

[FingRinal]

Making the shed or outbuilding TT (earth rod) simplifies the earthing requirements at the shed/outbuilding, especially if the main supply is PME.

Trying to fathom out the requirements leaves elecricians divided much like a group of blokes down the pub trying to decide whether Marciano or Louis was the greatest champion.

The easiest way to settle things is to buy a copy of IEE Guidance Note 8 Earthing and Bonding. It's all in there, perfectly explained.